1. Field of the Invention
The present invention relates to a composite of flat conducter elements having solder shunting areas. The present invention also relates to the use of this composite in sensor elements.
2. Description of the Related Art
The composite of flat conductor elements, for example of printed circuit boards or conductor foils, is employed in large numbers in many areas of electronics. In connection with sensor elements in particular it is quite often necessary to connect the actual sensor to the electronic evaluating device by such a composite. Often the sensor structures are embodied as strip conductors on printed circuit boards which can be made, for example, of glass. The connection with the electronic evaluating device then often is made via strip conductors on a flexible conductor foil. The printed circuit board and the conductor foil are then usually connected by a contact soldering method, in particular the smoothing solder method, in such a way that the respective strip conductors are in electrical contact with each other.
In order to satisfy the tendencies for miniaturization in the electronic field, the strip conductors, or the so-called solder pads, are arranged at continuously shrinking distances from each other. Solder pads are the areas in which the contact faces of the strip conductors of the respective solder partners are arranged. The smoothing solder method often is employed for contacting strip conductors arranged on two flat printed circuit boards, or conductor foils, as already mentioned above. In the course of this a solder deposit is placed on a solder pad of at least one of the two solder partners, wherein the volume of the solder deposit, i.e. the amount of solder, can naturally only be applied with limited accuracy within the range of definite tolerance values. Even with a galvanically applied solder deposit the actual volume of the solder deposit can fluctuate by up to 50%.
Depending on the type of application and technical realization capability, the solder deposit is often provided on only one of the solder partners. For achieving a high quality solder connection, the volume of the solder deposit must be applied, defined as accurately as possible, as a solder coating to the respective solder pad. After the solder deposit has been applied to the solder pads of at least one of the two solder partners, the two solder partners are placed on top of each other in exact positions. Thereafter, in accordance with the smoothing solder method, the solder depots are melted by a hot soldering plunger while the solder partners are pressed together. If now, because of process-related fluctuations, the volume of the applied solder is too large, the excess solder will exit the area of the solder pads, which can lead to the formation of short circuits between the strip conductors, so that the entire composite becomes unusable. Therefore the distances between the solder pads cannot be arbitrarily reduced.
Strip conductor arrangements are disclosed in Utility Model DE 295 17 067 U1, which have enlarged surfaces for receiving the excess solder.
The reduction of the distances between the strip conductors in such a composite is also limited in Utility Model DE 295 17 067 U1 because the shunting area for excess solder is arranged transversely to the strip conductors, i.e. in the direction of the distance which is to be minimized. Furthermore, in the embodiment of Utility Model DE 295 17 067 U1 the solder can spread unhampered transversely over the entire surface of the solder pad, even if the volume of the applied solder is relatively small within the tolerances, for example. In this case there is a tendency of too little solder material being available on the actual contact face.